Numerous esters and polyesters are known. Many are described as being useful as additives for lubricants and fuels. Illustrative examples of patents containing such disclosures include the following:
U.S. Pat. No. 2,540,570 teaches glycol or thioglycol esters of fatty acids, rosin acids, tall oil acids, etc. which are sulfurized or phosphorized. They are said to perform as extreme pressure additives in lubricants.
Esters of di- and tribasic carboxylic acids, having alkenyl substituents are prepared by esterifying the corresponding acid with primary monohydric alcohols or with monohydric alcohols containing oxygen or sulfur in ether or thioether linkages. These monomeric compounds are also taught as being suitable for use as lubricating oils.
U.S. Pat. No. 2,575,195 describes complex esters prepared by reacting one mole of a dibasic acid with one mole of a glycol in such a manner that a half ester is formed, after which the terminal hydroxyl and carboxyl groups are esterified with a monobasic acid and monohydric alcohol, respectively.
U.S. Pat. No. 2,575,196 teaches complex esters prepared by reacting one molecular proportion of a monobasic aliphatic acid with one molecular proportion of a glycol, forming a half ester of the glycol, after which two molecular proportions of such half ester are reacted with one molecular proportion of a dibasic aliphatic acid. The products of these patents are taught as being useful as synthetic lubricants and for use with mineral lubricating oils to give lubricants of improved viscosity index and pour point.
In U.S. Pat. No. 2,610,202 a compound made by reacting maleic anhydride with beta-mercaptoethanol is further reacted with a normal primary alcohol.
U.S. Pat. No. 2,929,786 teaches polyesters prepared from dibasic acids, or their esters, and glycols, including glycols containing thioether linkages. These compositions are said to be useful as additives or blending components in synthetic lubricant compositions.
A wide variety of esters of alkenyl succinic acids and anhydrides thereof are described as deposit modifiers for substantially hydrocarbon fuels. The esters are of mono-, di- and polyfunctional alcohols including mercaptoalkanols. U.S. Pat. Nos. 3,045,042 and 3,117,091 teach monomeric partial esters prepared by the reaction of alkyl or alkenyl succinic anhydrides with diols, triols or other polyhydric compounds including thiodiethanol.
Ester derivatives of hydrocarbon-substituted succinic acids containing at least about 50 aliphatic carbon atoms in the hydrocarbon substituent, which esters are prepared from monohydric and polyhydric alcohols, phenols and naphthols, are useful as additives in lubricating compositions, fuels, hydrocarbon oils and power transmitting fluids as well as being plasticizers, detergents, anti-rust agents and emulsifiers. Such materials are described in U.S. Pat. No. 3,522,179.
Functional fluid compositions containing ester additives derived from hydrocarbon substituted (which substituents include substituted hydrocarbon, preferably sulfur-substituted hydrocarbon) succinic acid and thio-bisalkanols are described in U.S. Pat. No. 4,702,850.
Each of the above-referenced patents is hereby expressly incorporated herein by reference for relevant disclosures contained therein.